One year after Elon Musk unveiled his grand plans to send humans to Mars, the SpaceX CEO is ready to make some refinements. Musk is returning to the same annual space conference where he made that original announcement, the International Astronautical Congress, to detail the new version of those plans. His speech starts tonight at 12:30AM ET (September 29th), and you can watch it above (or right here on YouTube).

We already know Musk’s revamped solar system colonization plan will now include a focus on the Moon, because earlier this evening he posted a rendering of a SpaceX Moon base on Instagram. The photo shows two of the company’s futuristic Mars Colonial Transporters sitting on the surface of the Moon with the Earth in the background.

How different will this new plan be?

What we hope to learn during his speech is not just what Musk thinks SpaceX could do on the Moon, but the reason for this recapitulation. After all, it was at last year’s IAC that he said that a permanent human presence on the Moon would be “challenging.” It could be a commercial play — after all, going to the Moon would be cheaper, and Musk has openly joked that he’s not sure how he will fund this massive spaceship or the launcher it requires. It could also be a nod to the shifting winds of the space industry, which have changed thanks to the priorities of the Trump administration.

Fear not, though, Mars fans. Musk also showed off a rendering of a “Mars city” on Instagram this evening, and so he likely has lots more in store for the speech. (This is an eccentric billionaire we’re talking about, after all.) There are also tons of questions still left unanswered from last year’s presentation. If you want to get educated — or speculate — while you wait, our own space reporter Loren Grush broke down what to expect from tonight’s talk earlier this week.